EPA promulgated emissions standards for Other Solid Waste Incineration (OSWI) units on December 16, 2005. Units covered under this rule include certain very small municipal waste combustion and institutional waste incineration units. On September 14, 2018, the U.S. District Court for the District of Columbia ordered EPA to “review and revise” the OSWI standards and guidelines and publish a notice of proposed rulemaking by August 31, 2020, and promulgate a final rule by May 31, 2021 (later extended to June 30, 2025). On August 31, 2020, the EPA proposed changes to OSWI subcategories and related maximum achievable control technology (MACT) floor redeterminations, applicability-related changes, testing and monitoring flexibilities for certain small OSWI units, among other proposed changes. Based on comments received after proposal, EPA is proposing to add a definition for a rudimentary combustion device and postpone standards for devices that meet the definition. This proposed action reflects feedback and consultations with the State of Alaska and Tribal representatives, including a webinar, informational meetings, consultation letters, and government-to-government consultations. The Agency heard that many of the rural tribal communities in Alaska use rudimentary combustion device, have limited financial resources and limited access to haul waste to a larger community.